Clutch shoe construction and method of making same

ABSTRACT

An improved clutch shoe of the type that is mounted on the rotor of a centrifugal clutch for coupling engagement with an outer clutch housing. The shoe is formed by two similar L-shaped shoe half sections which are stamped of sheet metal. Each shoe half section has an arcuate-shaped configuration comprising a web and an integral outer shoe table portion with an annular boss formed on each of the webs. A plurality of annular projections are formed to one of the shoe half webs and extend outwardly therefrom in a direction opposite from the annular boss formed on the web. The other shoe half web is formed with a plurality of holes into which the annular projections are press fitted to connect the two shoe halves together with the webs being placed in abutting relationship. The shoe half table portions lie in juxtaposition with respect to each other and form an outer shoe table on which a strip of friction material is attached. The annular bosses align with each other when the shoe half sections are connected and form a cylindrical sleeve into which a mounting bushing is press fitted. The method of stamping the shoe half sections, projections and bosses from sheet metal followed by the step of press fitting the projections into the complementary-shaped holes, followed by the press fitting of a mounting bushing into the aligned annular bosses elminates any welding, brazing, riveting or similar procedures heretofore required for connecting the shoe components.

TECHNICAL FIELD

The invention relates to a centrifugal clutch of the type having a pairof pivotally mounted clutch shoes which swing outwardly into couplingengagement with a driven clutch member automatically by centrifugalforce. More particularly the invention relates to an improved clutchshoe construction and the method of making it which has a reduced numberof components and manufacturing operations than heretofore required informing a similar type of clutch shoe.

BACKGROUND ART

There are numerous types and arrangements of centrifugal clutchconstructions in which one or more clutch shoes are retained inretracted position by springs until sufficient centrifugal force acts onthe shoes to overcome the force of retaining springs, whereupon theclutch shoes pivot and swing outwardly and engage a stationary clutchhousing or drum.

Many of these clutch constructions have a pair of arcuate shaped clutchshoes which are pivotally mounted on a clutch backing plate or rotor andwhich are arranged in an end-to-end relationship with respect to eachother. The backing plate usually is fixed to a drive shaft or hub forrotation with the drive shaft. These clutch shoes have various springarrangements which bias the shoes toward and retain the shoes inretracted position. It is this spring retaining tension which isovercome by the centrifugal force enabling the clutch shoes to engagethe driven member.

These clutch shoes have a variety of configurations and constructions.Each shoe generally has an arcuate-shaped member formed of stamped steeland consists of a flat shoe web with an outer curved shoe table on whicha strip of friction material is mounted for frictionally engaging adriven drum. In order to reduce the cost of these clutch shoes, fewercomponent parts and steps of assembly is desired without sacrificingreliability and efficiency.

Many types of existing clutch shoes are formed by a pair of similar,stamped steel flat members which are welded or riveted together to formthe shoe web. An arcuate strip then is welded to the outer edge of theformed web to provide the shoe table on which the friction strip isattached. These clutch shoes are pivotally mounted on the clutch backingplate by a pin or bushing which is telescopically mounted in a sleevewhich is welded or brazed in an opening formed in the shoe web.

This construction and method of assembly requires at least four separateparts, namely, a pair of matching shoe webs, an outer shoe table, and abushing mounting sleeve. Likewise, several welding, brazing and/orriveting operations are required for assembling these four components.Each of these separate components and the manufacturing and assemblingthereof increases the cost of the final clutch shoe construction.

There is no known existing clutch shoe construction and method of makingof which we are aware, that enables the clutch shoe to be formed by apair of stamped steel members which are joined without welding orbrazing operations, and which eliminates the use of a bushing mountingsleeve.

DISCLOSURE OF INVENTION

Objectives of the invention include providing an improved clutch shoeconstruction for use in a centrifugal clutch in which the shoe is formedof two complementary-shaped, stamped steel members which are joinedtogether without riveting, brazing or other similar attachment means;and in which each member has an arcuate, generally L-shapedconfiguration, one portion of which is the shoe web and the otherportion being the shoe table. Another objective is to provide such aclutch shoe in which one of the members is formed with a plurality ofoutwardly extending projections which are press fitted intocomplementary-shaped holes formed in the other member for joining themembers together to form the clutch shoe; in which each of the shoetable portions of the L-shaped member lies in juxtaposition to eachother to form the complete arcuate-shaped shoe table; and in which eachof the clutch shoes is formed with an annular outwardly projecting bosswhich align with each other when the shoes are joined to form acylindrical sleeve for receiving a mounting bushing therein.

Another objective of the improved clutch shoe construction is the pressfitting of the clutch shoe mounting bushing in the sleeve formed by thealigned annular bosses eliminating welding or brazing of the sleeve inthe shoe web as heretofore required. Another objective is to providesuch a construction which requires only two L-shaped stamped steelcomponents for forming the shoe, yet which enables an extremely durableand rugged shoe to be formed with a minimum of manufacturing procedures,and in which the shoe can be mounted in existing clutch constructionsusing the heretofore clutch shoe which was assembled from four or moreseparate parts and which had to be welded or brazed to assemble thesame.

Another objective of the invention is to provide an improved method forproducing the clutch shoe which reduces the number of manufacturingoperations heretofore required, and which eliminates welding, brazingand riveting operations without sacrificing reliability of the finishedclutch shoe. A further objection is to provide such an improved methodin which two L-shaped metal members are stamped from sheet steel with aplurality of annular projections being formed in one of the membersfollowed by the step of press fitting the projections intocomplementary-shaped holes formed in the other member to join themembers into an assembled shoe; and in which the improved method furtherincludes stamping annular bosses into the half shoe members, whichbosses surround openings; followed by the step of press fitting amounting bushing in the annular bosses after the half shoe members arejoined by the press fit engagement of the projections in the matingholes.

A further objective of the invention is to provide such a clutch shoeconstruction which is of an extremely simple arrangement, easy tomanufacture and assemble, sturdy and durable in use, which eliminatesdifficulties heretofore encountered with other known clutch shoeconstructions, which achieves the objectives indicated and solvesproblems, and which satisfies needs existing in the art.

These objectives and advantages are obtained by the improved centrifugalclutch shoe construction of the invention, the general nature of whichmay be stated as including first and second arcuate-shaped shoe halves,each having a web and an integral outer shoe table portion extendingoutwardly from said web; projection means formed on the web of one ofthe shoe halves and secured in complementary-shaped hole means formed inthe web of the other shoe half for joining the webs in abuttingrelationship; annular boss means formed on each of the webs for forminga cylindrical sleeve extending outwardly from said abutting webs; andbushing means telescopically mounted in the cylindrical sleeve formounting the shoe construction on a backing plate.

These objectives and advantages are further obtained by the improvedmethod of producing such a shoe construction, the general nature ofwhich may be stated as including the steps of stamping first and secondarcuate-shaped shoe halves, each having a generally L-shapedcross-sectional configuration with a web and an integral outer shoetable portion; forming a projection in the web of the first shoe halfwhich extends outwardly from the web in a direction opposite of the shoetable portion; forming a hole in the web of the second shoe halfcomplementary to the projection formed in the web of the first shoehalf; forming an annular boss and an interior opening surrounded by saidboss in each of the webs, said bosses projecting outwardly from the websin the same direction as the respective shoe table portion of the web;securing the projection formed in the web of the second shoe half toconnect said shoe half webs in abutting relationship, with the bosses ofsaid shoe half webs aligning with each other to form a cylindricalsleeve extending outwardly from said connected webs; and securing amounting bushing in the cylindrical sleeve formed by the aligned bosses.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention, illustrative of the best modein which applicants have contemplated applying the principles, is setforth in the following description and shown in the drawings, and isparticularly and distinctly pointed out and set forth in the appendedclaims.

FIG. 1 is a front elevational view of a centrifugal clutch shown inretracted position within a clutch housing which is shown in section,with the improved clutch shoe incorporated therein;

FIG. 2 is a sectional view taken on line 2--2, FIG. 1;

FIG. 3 is an elevational view of the improved clutch shoe constructionremoved from the clutch of FIGS. 1 and 2;

FIG. 4 is an end elevational view looking in the direction of arrows4--4, FIG. 3;

FIGS. 5 and 6 are end elevational views of the two half-shoe componentswhich form the improved clutch shoe;

FIG. 7 is an enlarged fragmentary sectional view taken on line 7--7,FIG. 3;

FIG. 8 is an enlarged sectional view taken on line 8--8, FIG. 3;

FIG. 9 is an enlarged fragmentary sectional view taken on line 9--9,FIG. 3;

FIG. 10 is a fragmentary sectional view similar to FIG. 7 showing theclutch shoe mounting bushing press fitted into the cylindrical sleeveformed by the joined half-shoe components;

FIG. 11 is an enlarged fragmentary sectional view similar taken on line11--11, FIG. 1; and

FIG. 12 is a perspective view of the clutch shoe mounting bushing.

BEST MODE FOR CARRYING OUT THE INVENTION

The improved clutch shoe construction is indicated generally at 1, andis shown in FIG. 1 mounted in a clutch indicated generally at 2. Clutch2 is intended to be driven in a usual manner by power shaft (not shown).Clutch 2 includes a rotor assembly 3 and a driven clutch member orhousing 4.

Housing 4 is shown as an integral pulley clutch housing having amulti-V-grooved pulley end formation 5 which is connected to acylindrical housing drum wall 6 (FIG. 2). The inner surface 7 of drumwall 6 provides a coupling surface for drivingly connecting clutchhousing 4 with rotor assembly 3. Housing 4 may have variousconfigurations and arrangements and may be adapted to be operativelyengaged with mechanisms other than a multi-V-grooved pulley belt withoutaffecting the concept of the present invention.

Rotor assembly 3 (FIGS. 1 and 2) includes a hub 9 which is adapted to bemounted on and secured to a drive shaft by a key-keyway arrangement orother attachment means so as to rotate with the drive shaft. Hub 9 has asmooth cylindrical inner bore 10 in which the drive shaft istelescopically inserted. Hub 9 further includes a reduced end 11 whichis provided with a cylindrical outer surface on which driven clutchhousing 4 is rotatably mounted by a bearing ring 12. Bearing ring 12 islocated between an inner annular shoulder 13 formed on hub 9 and a snapring 14 which maintains bearing ring 12 in position against shoulder 13.

The other end of hub 9 is provided with a cylindrical outer surface 15which terminates in an inner annular shoulder 16, which extends radiallywith respect to the central axis of rotor assembly 3. A rectangularbacking or drive plate 20 is mounted on the outer end of hub 9 andsecured against shoulder 16 by welding or other attachment means. Theabove-described clutch rotor assembly and construction is by way ofexample and may vary without affecting the concept of the improvedclutch shoe construction.

Improved clutch shoe 1 (FIGS. 3 and 4) includes two arcuate-shaped shoehalves, indicated generally at 25 and 26, as shown in FIGS. 5 and 6,respectively. Each clutch shoe half is generally L-shaped in crosssection having arcuate-shaped webs 27 and 28, terminating in integralshoe table portions 29 and 30, respectively. Shoe table portions 29 and30 extend outwardly at right angles with respect to webs 27 and 28.

Web 27 of shoe half 25 is formed with a pair of spaced annular-shapedprojections 32 and 33 which extend outwardly from web 27 in a directionopposite to shoe table 29. An annular boss 34 also is formed on shoe web27 and projects outwardly therefrom in the same direction as shoe tableportion 29 and opposite of annular projections 32 and 33. Projections 32and 33 preferably are equal in diameter to each other and have a smallerdiameter than boss 34. Boss 34 is stamped from web 27 and the materialdisplaced to form boss 34 provides a cylindrical opening 35 within theperiphery of boss 34 (FIG. 7). Likewise, the formation of projections 32and 33 in web 27 forms holes 36 and 37 within the periphery ofprojections 32 and 33, respectively.

Shoe half 26 is complementary in shape and size to shoe half 25 and isformed with a pair of circular holes 39 and 40 complementary to theouter diameter of annular projections 32 and 33, respectively. Anannular boss 41 also is formed on web 28 of shoe half 26 and projectsoutwardly therefrom in the same direction as shoe table 30. Boss 41 iscomplementary in shape and size with boss 34 of shoe half 25 andsurrounds a cylindrical opening 42 equal in size to opening 35.

In accordance with another feature of the invention, shoe halves 25 and26 are assembled by placing shoe webs 27 and 28 in abutment withprojections 32 and 33 being press fitted into holes 39 and 40,respectively (FIGS. 3 and 4). This press fit firmly joins the two shoehalves together to provide a laminated clutch shoe without requiring anybrazing, welding or riveting operation as heretofore required in priorlaminated clutch shoe constructions. Shoe table portions 29 and 30 arelocated in juxtaposition and form a single shoe table indicatedgenerally at 44, to which is attached a strip 45 of friction materialwhich is shown in FIGS. 1 and 2.

When shoe half webs 27 and 28 are joined in abutting relationship,bosses 34 and 41 and cylindrical openings 35 and 42 thereof, align witheach other as shown in FIG. 7. Bosses 34 and 41 extend outwardly inopposite directions with respect to each other and form a cylindricalsleeve 47 having a cylindrical opening 48 extending therethrough.

In accordance with another feature of the invention, a mounting bushingindicated generally at 50 (FIG. 12), is telescopically mounted withincylindrical opening 48 of sleeve 47 by a press fit engagement with thewalls of annular bosses 34 and 41 (FIG. 10). Mounting bushing 50 is of ausual construction and preferably includes an outer cylindrical sleeve51, an inner concentric sleeve 53 and an elastomer annulus 54 which ismounted in compression between sleeves 51 and 53. This press fitengagement of bushing 50 in sleeve 47 eliminates the welding or brazingof a separate bushing sleeve in a circular opening formed in the shoeweb heretofore required in prior shoe constructions.

Bushing 50 enables improved clutch shoe 1 to be pivotally mounted ondrive flange 20 in a usual manner as shown in FIG. 11. A pin 56 having acylindrical shank 57 which terminates at one end in a reduced diametercircular head 58, is inserted through a complementary-shaped hole 59formed in drive flange 20. The outer diameter of pin 56 is complementaryto the inner diameter of bushing sleeve 53 and provides a sliding,pivotal connection therebetween. A bridge 60 having a generallyelongated oval-shaped configuration (FIG. 1) is mounted on the top ofpin 56 by a cap screw 61 which is engaged in a threaded hole 62 formedin pin shank 57.

For most clutch constructions, a pair of clutch shoes 1 are mounted ondrive flange 20 as shown in FIGS. 1 and 2, and are arranged in anend-to-end relationship and are retained in retracted position by acurved strip of spring steel 65. Spring 65 is mounted on and extendsbetween adjacent shoe ends as shown in FIGS. 1 and 2 by spring pins 66.Each clutch shoe preferably is formed with a flat surface 68 at pivotalend 69 thereof which is engaged by a rounded projection 70 formed onswinging end 71 of the clutch shoes. The engagement of edge projection70 against flat surfaces 68 of the adjacent shoes serves as a stop forthe shoes when they are in retracted position. This eliminates the useof separate stop members as required in prior clutch constructions tolimit the inward movement of the shoes by the biasing effect of springs65.

In addition to the improved construction of clutch shoe 1, the method offorming the same reduces manufacturing costs by eliminating certainmanufacturing operations heretofore required in forming prior clutchshoes. The improved method of the invention includes the steps ofstamping shoe halves 25 and 26 in a metal stamping operation. Each shoehalf preferably is formed from a flat strip of metal with shoe tableportions 29 and 30 being bent at right angles with respect to theremaining arcuate webs 27 and 28 resulting in the generally L-shapedcross-sectional configuration shown in FIGS. 5, 6 and 8. Bosses 34 and41, annular projections 32 and 33, and holes 39 and 40 also are formedin webs 27 and 28 by metal stamping procedures, generally simultaneouslywith or in a separate stamping operation with the forming of the websand of shoe table portions.

All of above described steps can be performed by known stamping andmetal forming equipment in a single stamping operation or in aprogressive die arrangement. Shoe halves 25 and 26 can be producedextremely inexpensively in mass quantities, and then are assembledeasily by placing webs 27 and 28 in abutment with each other with bosses32 and 33 extending through aligned complementary-shaped holes 39 and40. Preferably projections 32 and 33 are press fit into holes 39 and 40with a sufficiently tight engagement to securely attach the shoe halvestogether in the abutting relationship as shown in FIG. 4. However, it iseasily seen that bosses 32 and 33 may have a looser fit in holes 39 and40 with the ends thereof, being staked or upset against web 28 to securethe webs together without affecting the concept of the invention.

The next step of the improved method is the press fitting of bushing 50in cylindrical sleeve 47 formed by the alignment of bosses 34 and 41 andopenings 35 and 42 thereof. Heretofore, a separate metal sleeve had tobe brazed in an opening formed in the shoe web to provide a sleeve forreceiving a mounting bushing. This separate sleeve had to be secured bywelding or brazing operations. This entire manufacturing operation hasbeen eliminated by the stamping of bosses 34 and 41 on webs 27 and 28.

Thus, the improved method provides an extremely simple and inexpensiveprocedure for forming a clutch shoe with a minimum number ofmanufacturing operations thereby reducing the cost of producing theclutch shoe without sacrificing reliability and operatingcharacteristics thereof. Furthermore, the improved clutch constructionrequires only two components for forming the clutch shoe in contrast tothe heretofore four components for forming a nearly identical shoeconstruction. The elimination of even one component part of a shoeassembly reduces the cost of the finished product.

Although the above discussion pertains to centrifugal clutches and shoestherefor, it is easily seen that this same shoe construction and methodof forming the same, will apply to brake shoes and their method ofmanufacture. The main difference between the two types of shoes is thatthe brake shoe moves outwardly into coupling engagement with anothermember by a hydraulic or mechanical force instead of under the influenceof centrifugal force as in the clutch construction described above.Therefore, the invention need not be limited to clutch shoes but willapply to brake shoes and the manufacture thereof. Likewise, projections32 and 33 are shown as annular members which are engageable incomplementary-shaped circular holes 39 and 40. These projections andmating holes may be non-circular, if desired, without affecting theconcept of the invention. Also, additional projections may be formed onthe webs at different locations than that shown in the drawings forsecuring the shoe webs in rigid abutting relationship.

Accordingly, the improved clutch shoe construction is simplified,provides an effective safe, inexpensive and efficient device whichachieves all the enumerated objectives, provides for eliminatingdifficulties encountered with prior devices and solves problems andobtains new results in the art. Likewise, the improved method providesan extremely simple and inexpensive manufacturing procedure forproducing such clutch shoe constructions by reducing the number andtypes of manufacturing operations heretofore required for producingclutch shoes.

In the foregoing description, certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirements of the prior art, because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration of the invention is by way ofexample, and the scope of the invention is not limited to the exactdetails shown or described.

Having now described the features, discoveries and principles of theinvention, the manner in which the improved clutch shoe is constructedand used, the characteristics of the construction, and the advantageous,new and useful results obtained; the new and useful structures, devices,elements, arrangements, parts, and combinations, are set forth in theappended claims.

What is claimed is:
 1. An improved clutch shoe construction of the typeadapted to be mounted on a drive rotor of a centrifugal clutch, saidshoe construction including:(a) first and second arcuate-shaped shoehalves, each having a generally L-shaped configuration with a web and anintegral outer shoe table portion; (b) a projection formed integrally onthe web of the first shoe half extending outwardly therefrom in adirection opposite to that of the shoe table portion; (c) an annularboss formed integrally on the web of the first shoe half surrounding anopening formed in said web, said boss extending outwardly from the webin a direction opposite of the projection; (d) a hole formed in the webof the second shoe half complementary to the projection formed on theweb of the first shoe half; (e) an annular boss formed integrally on theweb of the second shoe half surrounding an opening formed in said weband extending outwardly from the web in the same direction as the shoetable portion, said boss and opening being complementary to the boss andopening formed on and in the first shoe half; (f) the projection of thefirst shoe half being press fitted in the hole of the second shoe halfconnecting said shoe half webs in abutting relationship, with theannular bosses and openings of the shoe halves aligning with each other,and with the bosses extending in opposite directions to each otherforming a cylindrical sleeve extending outwardly from said connectedwebs; and (g) a mounting bushing having a cylindrical outer sleevetelescopically mounted with a press fit in the sleeve formed by thealigned bosses of the shoe halves.
 2. The clutch shoe constructiondefined in claim 1 in which the mounting bushing has an elastomerannulus telescopically mounted on an inner sleeve, with both the innersleeve and elastomer annulus being telescopically concentrically mountedwithin the cylindrical outer sleeve of the mounting bushing.
 3. Theclutch shoe construction defined in claim 1 in which the shoe half tableportions form a convexly curved outer surface when the webs areconnected in abutting relationship; and in which a strip of frictionmaterial is mounted on said curved outer surface.
 4. The clutch shoeconstruction defined in claim 1 in which the first shoe half webprojection has an annular configuration; and in which the second shoehalf web hole is circular and complementary to the outer diameter ofsaid annular projection.
 5. The clutch shoe construction defined inclaim 1 in which there are two projections formed on the web of thefirst shoe half and two complementary-shaped holes formed in the web ofthe second shoe half for joining said webs in abutting relationship. 6.An improved shoe construction of the type adapted to be mounted on abacking plate having friction material mounted on a convexly curvedouter edge thereof, said shoe including:(a) first and secondarcuate-shaped shoe halves, each having a web and an integral outer shoetable portion extending outwardly from said web; (b) projection meansformed on the web of one of the shoe halves and secured incomplementary-shaped hole means formed in the web of the other shoe halffor joining the webs in abutting relationship; (c) annular boss meansformed on each of the webs for forming a cylindrical sleeve extendingoutwardly from said abutting webs; and (d) bushing means telescopicallymounted in the cylindrical sleeve for mounting the shoe construction ona backing plate.
 7. The shoe construction defined in claim 6 in whichthe projection means extends outwardly from the web in a directionopposite of the shoe table portion.
 8. The shoe construction defined inclaim 6 in which the boss means extend outwardly from the webs in thesame direction as the shoe table portions.
 9. The shoe constructiondefined in claim 6 in which the projection means is a pair of annularprojections and the hole means is a pair of circular holes.
 10. The shoeconstruction defined in claim 9 in which each of the annular projectionsis formed integrally with the web from displaced material therefromthereby forming a hole in the web surrounded by said projection.
 11. Theshoe construction defined in claim 6 in which the projection means issecured in the hole means by a press fit; and in which the busing meansis secured int he sleeve by a press fit.
 12. The shoe constructiondefined in claim 6 in which the outer shoe table portions lie injuxtaposition to each other when the webs are joined in abuttingposition and form the convexly curved outer edge for receivably mountinga friction material thereon.